I've been playing around with the retirement calculator on Fidelity's website, and I find that it seems to ask for a reasonable amount of information, and then runs the simulations. I like that I can play with the various parameters, and see how changes impact the results.

I've actually been using it to test when we should take Social Security, as we are close enough now (within 10 years) that I think I can reasonably count on it still being there.

That said, I've been trying to figure out what number I should use for post-retirement expenses. I actually have a written budget, and it starts with our total needs, and then does some calculations based on today's tax laws to figure out how much I need to withdraw including taxes. So which number would you use in the Fidelity calculator? Would you use the number that does or does not include the taxes? It seems to make a significant enough difference that I'd like to know which I should be using.

And yes, I realize it is just an estimation, but it's still a good model, and can get me close enough at this point.